I have a roof rake onmy caravan and it has 2 cross braces that are adjustable front to rear. Now usually one is all the way forward and the other is all the way back. Now my question is, Where is the best position for the 2 for best mileage/ lowest drag?

One far forward and the other far back?
One in the middle and the other far back?
Both far forward?
Both far back?

How can I test this? I was thinking about taping some this gift wrapping ribbon to the trailing edge of the windwhield and watching how it flows over the roof.

I have a roof rake onmy caravan and it has 2 cross braces that are adjustable front to rear. Now usually one is all the way forward and the other is all the way back. Now my question is, Where is the best position for the 2 for best mileage/ lowest drag?

In the trunk or in the garage.

Seriously, roof racks, especially cross-braces, create tons of drag. I assume the rails would be a pain to remove and reinstall, but the cross-braces usually aren't that difficult to remove. Only have them there when they are in use.

Caravan roof rack cross braces are already streamlined. On the '97, the track release is at the front of the side rails. Flip the streamlined fairing forward (they're hinged at the front) and the cross braces will slide forward off the rails.

There is no good way to remove the side rails without gutting the headliner, and then you loose the option of using the roof rack ever again. I have contemplated filling in the gap under the side rail with some kind of foam/urethane/stuffings. This can be done without interfering with the operation of the cross braces. But I suspect the effectiveness would way down the list of things you could do. The first thing on that list is take the cross braces off.

I can't figure out how to take the crosspieces off my '88 without trashing the rack completely (Well not trashing it, but making it a major event to put back on again) I use it a couple or three times a year and don't want it disabled, and half the times I use it are somewhat unplanned...

Anyway, I have had mine set as far forward as they go for the last couple of months... I was visualizing them helping to straighten the airflow and "nail" it back down to the roof again after it came off the screen, while also making a high point for the air going over them, such that the roof acted as a more rounded shape and air was coming over the tailgate at a slight angle.

I'm planning to make stick on fairings out of quartered pool noodles to blend my rails. Held on with industrial style velcro.

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The other thing I just found at the junk yard (weekend is not complete if I haven't gone junking) was an intact Caravan air dam ($4). The Caravan air dam would seem to be reasonably effective for a production car, wide and low, but they tend to get torn off by parking blocks, usually taking the bumper with it. I'm going to put the air dam on and then put curb feelers on the bumper to try and keep the dam intact. Then I'm thinking of putting a segmented extension on that to make it lower and wider. The segments will allow the sections fold back and forth without being torn up.